RO Membrane Central Tube Specifications
These RO membrane central tube specifications cover the material, sizes, hole pattern and connection of the permeate (collection) tube that forms the core of every spiral-wound element.
- MaterialABS / PP / Noryl
- RoleCollects permeate
- Sized toElement model
- Also calledPermeate tube
What the Central Tube Does
The central tube — also called the permeate tube, product water tube or collection tube — runs down the axis of the element. The membrane leaves spiral inward and glue to it, and permeate flows through holes in the tube wall and out the end. It is both a flow path and the structural core the element is wound around.
For the basics of how it works, see what the central tube is. Its size is set by the element model — check the element size reference when matching one.
Central Tube Specifications
Typical specifications for RO membrane central tubes. Exact dimensions are set by the element model and confirmed per order.
| Property | Typical specification |
|---|---|
| Material | ABS, polypropylene (PP) or Noryl (PPO), depending on application |
| Function | Collects permeate and forms the structural core |
| Sizing | Inner/outer diameter and length set by element model (1812 to 8040) |
| Hole pattern | Rows of permeate-entry holes along the wound section |
| Length | Matches element length plus connection allowance |
| Connection | Suited to the interconnector / end-cap system — [confirm per design] |
| Pressure rating | Sufficient for the element’s operating pressure — [confirm per material] |
| Also known as | Permeate tube, product water tube, collection tube |
Matching a Central Tube
The central tube must match the element size, the hole pattern your process expects, and the connection at each end. Get the diameter or length wrong and the leaves will not glue correctly or the element will not connect in the vessel.
Match it alongside the rest of the build with the production setup guide, and see how all materials fit in the raw material selection guide.
Match to your element
- Diameter & length by element model
- Hole pattern for permeate entry
- Material vs operating pressure
- Connection / interconnector system
- Clean bore for taping & gluing
The Core Sets the Whole Build
Everything winds around the central tube, so an error here is hard to recover later in the build.
Wrong Size
An off-size tube means leaves do not glue cleanly and the diameter drifts.
Weak Material
Under-rated material can deform under pressure and leak at the core.
Bad Connection
A mismatched connection stops the element seating correctly in the vessel.
Need central tubes for your elements?
Tell us your element sizes and connection system — we’ll supply central tubes matched to your build.
Central Tube FAQ
What is the RO membrane central tube made of?
Central tubes are typically made of ABS, polypropylene (PP) or Noryl (PPO). The material is chosen for strength at the element’s operating pressure and compatibility with the permeate.
Is the central tube the same as the permeate tube?
Yes. Central tube, permeate tube, product water tube and collection tube all refer to the same part — the perforated core that collects permeate and that the element is wound around.
How do I choose the right central tube size?
The diameter, length and hole pattern are set by the element model (1812 to 8040) and your connection system. Use the element size reference to match the size, then confirm the exact tube specification for your build.
Why does the central tube have holes?
The holes let permeate that has spiralled inward through the membrane envelopes enter the tube, where it collects and flows out the end of the element as product water.